In the paper and label processing industry, webs or sheets of material are transversely cut or perforated by relatively thin, flat blades. These blades are often mounted in a slot of a cutter or blade cylinder and clamped in the slot with a blade holding bar, also referred to as a blade bar. The blade cylinder is rotated and typically cooperates with a rotating hardened anvil cylinder or a fixed knife to effect the cut "on the fly" as the web moves, either supported by the anvil cylinder or moved over the fixed knife.
For many years, the blade was removably secured in a slot in the blade cylinder by threaded fasteners. As a result, it took approximately six minutes to change a worn blade and, further, a relatively high degree of operator skill was required to set properly the operating blade height and to clamp the blade. These delays are costly since a production line is shut down for the blade change.
Since the 1980s, companies have offered blade clamping bars with a significantly faster blade change interval; however, these bars still require considerable care and skill from the operator. Subsequent improvements disclosed in U.S. Pat. Nos. 5,086,683, 5,211,096, and 5,224,408 include a holding bar which allow a blade change in approximately six seconds and offer simple and automatic clamping as well as convenient adjustment of the height of the blade over small increments. The height adjusting feature of this apparatus allows the blade effectively to cut a variety of materials such as glassines, polyester, paper, and release liner while maximizing blade life, reducing blade change time, simplifying height adjustment of the new blade, and making the adjustment accurate.
The height-adjusting and accuracy features are advantageously practiced by means of a two-piece slide forming a split ramp which fits into a slot in the bar having a corresponding incline or ramp. As the slide member is adjusted axially of the blade cylinder relative to the other slide member, the cooperating ramp surfaces of the two slide members raise or lower the bar and, because the blade is carried by the bar, the blade is raised or lowered, as well.
The height-adjusting just described does not permit adjustment of the tilt of the blade. If the bottom surface of the slot in which the bar is installed is not parallel to the cutting surface of the anvil cylinder, for example, the blade supporting ledge of the bar and, hence, the cutting edge of the blade are not parallel to the surface of the adjacent anvil cylinder. The result is that the blade does not cut evenly across the web or sheet. The bottom of the slot may have some amount of non-parallel condition due to errors in machining the slot. Other sources of this non-parallel condition are small, but inevitable, errors in machining bearing blocks and bearing bores, and errors in aligning the side frames which typically support cutting cylinders. Until the advent of the height-adjusting bar, the parallel condition of the bottom of the slot was of minimal importance and was often not specified precisely.
In the past, the non-parallel slot condition was addressed by installing layered shim material under the bar. Layers of the shim material are peeled back and trimmed to provide an approximation of the non-parallel condition; and the shim is installed between the bar and the bottom surface of the slot to compensate for the out-of-parallel error, regardless of its cause. This compensation is effective, but it requires a relatively skilled technician to estimate the amount of non-parallel error and to configure and place the layered shim properly. Sometimes, even a skilled operator must make and try several different shims before the non-parallel condition is corrected. Moreover, the bar needs to be removed from the slot to insert the shim, and this consumes additional time. The layered shim does not provide the ideal condition of continuous support under the bar because the trimmed ends of each shim layer are slightly stepped and present a small discontinuity in support. Hence, the shim material tends to wear or `pound out` during use, and it requires replacement.
Prior blade support bars are typically 18" to 22" wide and have a single, continuous ramp which provides the desired range of blade height adjustment (typically.+-.0.015"). They also provide the desired range of height adjustment affected by a given amount of rotation of the adjusting tool. As bars are made wider to accommodate wider webs, however, a full-width, continuous slide is too tall at one end if it is to provide the necessary range of height adjustment. This results in one end of the slide protruding above the top of the bar. Or, on the other hand, if the slide tapers to zero at the other end, it would not be able to provide the necessary support under that end of the bar during the impact conditions of use.
To increase the width of cutter (or "blade") cylinders which the cutter bar can accommodate, a two-piece ramped slide assembly has been used with a multiplicity of shortened ramp sections. That is, each ramp section is identical, having the same incline and height range; and the ramp sections are placed side-byside to form the complete ramp. This sectional slide arrangement fits different bar widths, especially wider bars, without varying the incline angle of the ramp, thus preserving the desired range of height adjustment and the desired increment of adjustment per unit of rotation of the adjusting tool. The sectional ramp slide is a two piece assembly with precisely graded and matching ramp surfaces to provide nearly continuous support of the bar.
In the instant invention, a two-piece sliding adjustment bar with sectional ramps is used to effect height adjustment of the blade. In the preferred embodiment, the top of the upper slide is formed into a circular arc or curve having a large radius so that the total curvature over the width of the bar is small. A precisely matching circular arc is formed in the surface of the bar engaged by the upper slide member. An adjusting mechanism is provided which permits the operator to slide the upper slide member longitudinally of the bar (i.e., axially of the cylinder). As the upper slide member is moved longitudinally relative to the bar, the curved surface of the upper slide member moves along the corresponding curved surface of the bar, thus lowering the end of the bar from which the slide member moves away and raising the end of the bar toward which the slide member is moved. This motion, in turn, tilts the blade relative to the axis of the cylinder. In other words, shifting the upper slide member relative to the bar allows the bar (and the blade) to be angled relative to the bottom of the slot (and the axis of the cylinder), and thus provides the ability to compensate for, or cancel, any undesirable non-parallel condition that may exist between the slot bottom and the cylinder axis of rotation. This allows the desired, uniform cutting action across a web or sheet.
The instant invention also includes apparatus for convenient, predictable angular adjustment (i.e., tilt) of the cutting bar, for maintaining the desired adjustment during operation, and for increasing the range of tilt adjustment.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.